1. Technical Field
Embodiments of the present invention relate generally to data storage and management and more particularly to a method, system, and apparatus for re-conveying input/output (I/O) operations utilizing a sequential-access data storage device secondary communication port.
2. Description of the Related Art
As the use of data processing systems has become more prevalent, the techniques used to store and manage data produced by such data processing systems have evolved. One mechanism for storing, providing access to, and processing such data is the data storage subsystem. A data storage subsystem includes an integrated collection of data storage controllers and/or host bus adapters, data storage devices, and any required control software used to provide data storage services to one or more data processing systems. Data storage subsystems can be simple or complex, large or small (in terms of physical structure and/or data storage capacity), ranging from a single data storage device, to an intelligent storage array, to a storage area network or storage domain thereof. Conventional data storage devices include machine-readable media (e.g., fixed disks, CD/DVD-ROMs, tapes, solid state memory, or the like) which may be fixed, removable, magnetic, optical, random/direct access, and/or sequential access as well as media loaders and robots utilized to access such media.
In a sequential-access data storage device (e.g., a tape data storage drive) data is organized and I/O operations are performed in a sequential fashion. In other words, individual I/O operations (e.g., read and write operations) are performed such that data is written sequentially in the order it is received and read sequentially in the order it is stored within associated sequential-access data storage media and device access occurs such that I/O operations are performed serially. In many sequential-access data storage devices, data access is provided via a single half-duplex communication port such as a small computer system interface (SCSI) or Fibre Channel (FC) port. Although sequential-access data storage devices have more recently been provided having additional communication ports, these additional ports have thus far been utilized strictly for failover/redundancy or to otherwise provide sequential and serial data access.
As data storage subsystems have developed, more and more functionality that was originally managed or performed by host data processing systems (e.g., servers) has been off-loaded to data storage devices and storage subsystem infrastructure. One example of this functionality shift is the use of “serverless” or “server-free” backups.
In serverless backup, an existing procedure or protocol such as the Third Party Copy Protocol provided by the Storage Network Industry Association (SNIA) or the Extended Copy (X Copy) Command as described in Information Technology—SCSI Primary Commands—4 (SPC-4), Working Draft, Revision 02, T10, a Technical Committee of the Accredited Standards Committee of the National Committee for Information Technology Standards (NCITS), Sep. 15, 2005 is utilized to copy or “backup” data from a first data storage device to a second data storage device without using a server data processing system for data transfer. Typically, serverless backup is performed using a SAN redistribution node (e.g., a FC switch) or an intelligent storage device (e.g., a disk storage array, tape data storage drive, tape library, or the like).
As a consequence of their data storage structure and access mechanism, the rate at which data stored within conventional sequential-access data storage devices may be accessed via “read” or “write” type input/output (I/O) operations, and consequently the rate at which more complex data storage and management operations such as serverless backup may be performed, are relatively slow as compared to other data storage device types (e.g., fixed disk, direct access storage devices).